The operation of a typical engine intake system is well known. In a typical internal combustion engine, air enters the engine's intake manifold through a throttle body. The throttle body generally has one throttle valve that regulates the amount of air entering the intake manifold. Once the air is inside the intake manifold, it flows through the intake manifold's air passages into the combustion chambers of the engine. In the intake manifold, the air mixes with fuel, and the air/fuel mixture is introduced into the combustion chambers of the engine for combustion.
How well the air and fuel is mixed directly affects engine performance in terms of efficiency and emission, and is affected by how the air flows through the intake manifold. Therefore, the air passages of the intake manifold are configured to achieve a thorough mixing of the air and fuel and to enhance engine performance. However, different engine operating conditions, especially different engine speeds, require different air passage configurations for maximum engine performance. Therefore, the air passages of the intake manifold are often configured to achieve a balanced engine performance over the entire range of engine operation, but less than optimum engine performance at each engine operating condition.
For these reasons an airflow control valve assembly is provided to adjust the airflow through the intake manifold to account for different engine operating conditions, in particular to promote a thorough mixing of air and fuel at low engine speeds without sacrificing engine efficiency at high engine speeds.
Typically, the airflow control valve assembly has valve plates disposed, respectively, in the air passages of the intake manifold to adjust airflows through the air passages. The valve plates are mounted to a common valve shaft for rotation about the shaft's axis. An actuator, controlled by an electronic control unit, rotates the valve plates between an open position and a closed position depending on the engine operating condition.
The actuator, such as an electric motor, is mounted on the casing of the intake manifold with screws. Additionally, the actuator is rotationally connected to the valve shaft so that the actuator's rotational movement can be transmitted to the valve shaft. The actuator can be connected to the valve shaft either directly or indirectly via a mechanism, such as a gear arrangement or a four-bar linkage. The mechanism is also mounted to the casing of the intake manifold with screws, and is rotationally connected to the actuator and the valve shaft to transmit the actuator's rotational movement to the valve shaft.